Republican Donald Trump has secured his nomination for US president on day two of GOP’s National Convention.

House Speaker Paul Ryan urged delegates to unite behind Donald Trump, a day after splits in the party were evident as the convention opened.

The Trump campaign also faces accusations a speech by Melania Trump on July 18 was plagiarized from First Lady Michelle Obama’s 2008 Democratic Convention speech.

On the second day of the Republican National Convention, speakers focused almost exclusively on attacking Hillary Clinton, the likely Democratic nominee.

New Jersey Governor Chris Christie, a former prosecutor, held a mock trial for Hillary Clinton as the crowd chanted “lock her up”.

Chris Christie and others criticized Hillary Clinton’s use of a private email account while she was serving as secretary of state.

An FBI investigation said Hillary Clinton was “extremely careless” but found her actions didn’t warrant criminal prosecution. However, Gov. Chris Christie and the crowd disagreed as he repeatedly yelled “guilty”.

Chris Christie said Hillary Clinton has “selfish, awful judgment” and was to blame for various foreign policy problems in Libya, Syria and elsewhere.

Donald Trump is expected to accept the nomination on July 21.

His children played a prominent role on July 19, standing with the New York delegation as he was declared winner and delivering remarks.

Donald Trump youngest daughter, Tiffany Trump, whose mother is former model and dancer Marla Maples, told some personal stories about her father.

Tiffany Trump recalled scribbling notes in her school report cards and how excited she becomes when introducing her father to her friends.

Donald Trump is a “natural-born encourager” who has motivated her to work hard, his daughter said.

His son, Donald Trump Jr., described him as his best friend and role model.

“When people tell him it can’t be done, that guarantees it will get done,” he said of his father.

Donald Trump Jr. said Hillary Clinton was a risk the US could not afford to take and that “if she were elected, she would be the first president who can’t pass a background check”.

Donald Trump addressed the audience via a live-stream and said the nomination was an honor.

“This is a movement, but we have to go all the way,” he said.

“This is going to be a leadership that puts American people first.”

Parts of Donald Trump Jr.’s speech used segments of an article that had already appeared in the journal The American Conservative.

However, the article’s author, FH Buckley, said it was not plagiarism, as Buckley himself acted as one of the family’s speechwriters.